A lot of treated-wood decks have been built in the last couple of
decades, and many people have become fed-up with the need to
frequently seal their wood deck surfaces. Many people don't bother
to seal their decks at all, and after a few years they begin to
wonder why their deck surfaces look so dreary, tired and weathered.
I've seen pressure-treated deck boards begin to rot after a decade
of rain washing off a nearby roof, perhaps because the frequent
water-torture dissolved some of the preservative chemicals.

There is a big movement towards alternatives to treated wood for
deck surfaces. There are many brands of synthetic or composite
decking available. This list
of web links shows some.

The 6' x 24' deck extension after the
framing had been completed and some of the handrail
posts had been installed.

The older part of the deck has already had
its deck boards replaced, by other people.

This is a TrapEase™ brand of
screw that is meant for fastening composite decking
material. The package claims that there is no need for
pre-drilling and there will be no
"mushrooming" around the screw head.

That was not my experience.

I used a big, low RPM drill to
drive these screws. My impact driver did the job but was
getting rather warm from all the activity, so I decided
to try a regular corded drill.

Mushrooms On Deck:

At first I just drove in the screws
without pre-drilling. It seemed that the screw heads
would stick up slightly and leave a small mound around
the head. This mound is called a "mushroom"

So I pre-drilled some holes with a drill-countersink
combination bit.

When I pre-drilled the holes the screws
sank in just fine, perhaps a little too deep.

By placing a straight-edge over the screw
head you can see the difference. The pre-drilled screw
heads were sunk fine with barely any visible
mushrooming.

But without pre-drilling it was another
story. You can see the mushrooming, because there is a
gap under the straight-edge.

But even worse, these screws just spun once
they got this deep, as though they had stripped out the
wood underneath. That did not give me a feeling
of confidence, though they seemed to hold okay.

After trying a few screws without pre-drilling, I decided to
pre-drill all the remaining screws. This added to the
installation time, perhaps doubling the time needed to fasten
the boards.

Obstructions:

Where the deck boards met a handrail post
I laid the board next to the post and marked the notch.
I also marked the end cut so the board would overhang
the end by one inch after a facing was installed on the
stair riser.

The home owner wants skirting installed around the
deck to conceal the space underneath, and the plan is to
use this same material for skirting.

Unlike yellow pine, this material is very easy to
straighten as it's being fastened. I just pushed on the
board with my knee.

I used nails to give me the required space
between boards. The instructions call for a 1/8 inch gap
at the sides and ends. I used thin siding nails
most of the time, but also some thicker 12d nails to
provide a greater space to correct the curvature
problem that was started by the guys that installed
the first batch of deck boards.

To straighten out the curvature, I placed
a scrap of deck boards at each end, separated by a thin
nail from the previous board, and snapped a chalk line
(red arrow) between the edges of the boards.

In the middle of the deck, there was an
obvious gap between the chalk line and the edge of the
new board.

Consequently, I used larger nails for spacers in the
middle of the deck. By doing this over several rows of
deck boards I was able to correct most of this curved
deck board problem without creating gaps that were
obviously uneven.

More Gap Issues:

Since the deck was almost 24 feet long, and the boards were 16
feet long, I had to pay attention to the way the boards
"broke", that is, the pattern of end gaps between
boards. It looks stupid if all the end gaps line up in a row.

There are many ways to handle this
problem. You can use random lengths of decking to create
a random patterns of end gaps, but with manufactured
decking that is impractical.

I alternated the gaps (red arrows) by starting one
row with the long board on the left edge, then
the next row would have the long board against the right
edge of the deck.

Break Down:

It would be entirely possible (and logical) to use a full 16'
board to extend from the edge of the deck to the exact center of a
joist, since 16 feet would land right on a joist center. BUT... not
my luck.

After framing this deck extension the homeowner told me
about wanting to use this same decking for a skirting material to
conceal the space below the deck, and he also decided to relocate
the stairs to a different side of the deck. Suddenly if I allowed a
full deck board to break on a joist I would not have enough
overhang at the edge to cover the skirting (one inch thick) and
provide the desired one inch nosing overhang that is normally used
on stair treads.

So the logical solution is to let the deck board break one joist closer
to the edge, and cutting each board shorter by about 14 inches. But
the 14 inch scrap would be wasted. So I decided to let the deck
boards break two joists closer to the edge, thus cutting each
board shorter by about 30 inches. Since this deck is about 20 to 24
inches above the ground, these off-cuts could be used for the
skirting material with only a few inches of wasted material.

If I could've used exact 16 foot boards, I could also use
a board that was just less than 8 feet for the remainder of the row,
which meant that a full board would give me two short pieces. This
was the plan... use 3 boards for two rows of decking. We had not
ordered much extra decking. It's common to buy about 10 percent
extra material for a job like this, but with expensive composite
decking that becomes undesirable. Besides, you don't need to discard
any bad boards, right?.

But when I cut the long boards shorter, the next board in the row
needed to be about 10 feet long, leaving a 6 foot off-cut. Knowing
that I would be using this deck material for the stairs, I set these
6-footers aside. It's amazing how a small oversight can cause
complications later, unless you have money to burn and don't mind
wasting expensive decking material.

At this point I was down to the last two
rows of decking, and I had one full-length board
remaining and numerous pieces around 6 feet long.

There are five handrail posts to notch around,
and both rows of decking need to be notched.

I cut a deck board to length and laid it
against the posts, then I marked the edges of the post
on the deck board.

I measured the distance from the previous
board to the deck post, in each location.

Then I measured across the deck board to
mark this dimension.

It's easy to get turned around here and draw this
mark measured from the wrong edge, resulting in a
notch that's way too deep, so stop and think about
things before you plunge into cutting notches.

I cut the notches with a jig saw. This material cuts just like
wood, with some minor differences.

The instructions say to leave a small gap
around posts.

The decking after completion. The outer
edge (far left) was made from 4 boards ranging in length
from about 6 to 8 feet.

I was lucky that the final row of decking did not need to be
ripped narrower. Before starting this project, the homeowner measured the width of the deck
extension, and pointed out that with small gaps between boards we
should be able to get the desired overhang (about 1½ inches) at the
final board by using only full-width boards.

If I had needed to rip the final board, it would have been
necessary to round-over the cut edge with a router or router table.

Most carpenters start installing deck boards at the
outer edge of the deck and work inwards, towards the house.
If the final board needs to be ripped narrower, then the cut can be
concealed next to the house (under the edge of the siding) or
perhaps it just won't be very noticeable.

Since the original part of this deck had already been covered
with deck boards, I was not able to begin installing deck boards at
the outer edge. If this backwards board installation method is
necessary, and there's not enough space for a full width (or nearly
full-width) deck board at the last row, then one or more deck boards
will need to be ripped narrower. It's important to avoid having a
really narrow deck board at the outer row, because it may be
impossible to fasten a skinny board. The trick is to figure out the
width difference needed and divide that width reduction over several
boards. Personally, I would try to keep all the deck boards at least
4 inches wide, so it may be necessary to rip the last 3 or 4 boards
narrower.

An Example: Suppose the outer board was destined to be
only 1-1/2 inches wide. With a 1-inch overhang requirement, that's
too narrow to fasten. Since these deck boards are 5-1/2 inches wide,
there is 4 inches of width reduction needed. By ripping the last 4
boards an inch narrower (resulting in 4-1/2" wide boards) the final
board will be plenty wide, and the slightly narrower boards might
not be noticeable.

Trimming The Ends Of The Boards:

Sometimes the best way to install decking is to simply let the
boards run a bit too long, then cut the ragged ends later.

I marked the ends for an overhang of just
over one inch (I would prefer more, but the other guys
didn't leave enough) then snapped a chalk line and cut
the boards with a circular saw.

After trimming the ends of the composite deck boards
I used a belt sander to round over the sharp corners.

Later we'll install this same composite
material for skirting to conceal the area below the
deck. Read about installing
deck skirting.

The completed project, after the stairs,
skirting and handrails
had been installed.